*Corresponding Author:

Prof. Mohammad Shoeb

Department of Chemistry, University of Dhaka, Dhaka-1000, Bangladesh, Tel: +8801715191988, Fax: +8802-9667222, E- Email: shoeb71@yahoo.com

ABSTRACT

The objective of the present study is to analyse quantitatively toxic metals such as arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr) and mercury (Hg) using atomic absorption spectrophotometer (AAS) in nineteen marine fish samples of thirteen species. The muscle of fish samples were freeze dried, digested by microwave digestion and finally analysed by AAS. The level of toxic metals varied significantly among fish species and showed that As, Cd, Pb, Cr and Hg levels of mean values were 0.03, 0.04, 0.20, 0.59 and 0.19 mg/kg, respectively. The range of As, Cd, Pb, Cr and Hg in fresh samples were ND-0.04, ND-0.19, 0.06-0.35, 0.42-0.78 and 0.01-0.61 mg/kg fresh weight, respectively. All the values were below the permitted limit set by FAO/WHO standard for each toxic metal except C. carati and L. equulus those contain Cr in excess and E. Tetradactylum that contain Hg in excess level. Quantitative analysis reveals that the marine fish samples are less contaminated than fresh water fish in Bangladesh.

Key Words: Marine fish; Bioaccumulation; Toxic metals; Toxicity; AAS.

Introduction

The Bay of Bengal, one of the largest marine ecosystems in the world is situated at the southern part of Bangladesh. It encompasses about 710 km cost line in south of Bangladesh having about 50 m depth with an area of nearly 37,000 km² and is an important source of marine fish. It was reported that 442 marine fishes, 22 amphibians, 17 marine reptiles are available in Bangladesh [1]. Millions of people are consuming marine fish as a vital source of animal based protein all over the world. Toxic metals may enter into human body through contaminated fish food products and will have harmful acute and chronic effects since fish and other food items are the predominant sources (>90%) of heavy metals and chemical contaminants [2]. Although living body required some heavy metals for their normal growth and development but in excess level of essential metals and most of the non-essential metals show toxic effects in living body [3]. So it is essential to know the contamination level of toxic metals in the marine fish samples. The contamination of fresh water as well as the marine environment for the disposal of toxic metals has become a global problem due to the indestructible nature and toxic effect in human body [4]. In many part of the world, waste from both the natural and anthropogenic sources like industries, geochemical structure, steel dust, and mining process of different metals, domestic sewage, discharge, and fossil fuel burning polluting water bodies and accumulate up to a toxic level in fish and create ecological problem [5]. Through the bioaccumulation and bio-concentration process after discharging toxic metals to the aquatic environment, the concentration of different toxic metals is increased in aquatic animal body than in water which shows toxic effect in human body after consumption [6]. Different routes such as adsorption, respiration and ingestion are responsible for the accumulation of toxic metals in the marine fish since they are the most vulnerable animal in the marine environment [7]. The nutrient and the contaminant levels in the marine fish samples are regulated by the age, location, life stage, seasons, diet and species and the bio accumulation level is higher in fish since they are at the top level of aquatic food chain [8]. Bioaccumulation level of toxic metals in marine fish is an indirect measure of the pollution monitoring program in the marine ecosystem [9]. Although a large number of fresh water fish samples were analysed in the previous year in Bangladesh for the presence of toxic metals [10-13] study of marine fish samples from Bangladesh is rarely encountered. Therefore, the objectives of the present study were to determine contamination level of toxic heavy metal in fish samples available in Bangladesh.

Materials and Methods

Sample Collection

Samples were collected randomly from three different markets i.e., Fishery Ghat, Kazir Daori and Reazuddin Bazar in Chittagong near to the coast of the Bay of Bengal (Figure 1). The selected fishes (Table 1) are the most abundant and commercially important species consumed by the people.

Sample Preparation

A clean washed high quality corrosion resistant stainless knife was used to cut off the fish tissue (muscle). After dissection, all the samples were labelled according to their species. The entire samples were separately dried taking 10g of each in freeze drier in the laboratory until the constant weight is obtained. The dried samples were each ground with laboratory ceramic mortar and pestle to powder and stored in aluminium foil paper and kept in desiccators until analysis.

Sample Digestion Procedure

A certain amount of dried fish was taken in a tarred silica dish and put in a furnace consecutively at 100, 200, 300, 400 and 500 ºC temperatures each for 1 hour until the sample become ash. Toxic metals (As, Cd, Pb, Cr and Hg) were analysed after digesting the definite amount (5-10g) of homogenized samples in a mixture of concentrated HNO3 (20 mL) and H₂O₂ (10mL) and heat it on a hot plate until a transparent clear solution is obtained. The solution was made up to the mark in 50 mL volumetric flask. After filtration the solution was analysed in AAS. For As analysis, the ash was dissolved in 1:1 HNO₃: H₂O₂ solution. The sample was then taken at hot plate to remove acid vapour. Again it was heated directly at 500ºC temperature until full ashing. 5-10 mL HNO₃ was added to the sample and heated in normal burner. While heating, a little amount of water was added and cooled. The sample was then taken into a 25 mL volumetric flask by filtering and made up to the mark. 5 mL of the sample was taken in another 25 mL volumetric flask and 2.5 mL of conc. HCl and 0.1% KI was added to it. It was then made up to the mark with deionized water and kept overnight.

After developing yellow color the solution was used for analysis in AAS. The toxic metals detection was performed by following standard methods APHA, AWWA, WPCF [14] using Atomic Absorption Spectrophotometer (AAS). After preparing the standard solution of different metals, each solution was run in AAS.

Using these data and the concentration of each standard solution five calibration curves were made for five different toxic metals. All curves gave straight line with their respective correlation coefficient (R²). The limit of detection (LOD) was calculated by taking peak height (concentration of the standard) three times of noise level (S/N; 3:1; Table 2). Following these curves the amount of different toxic metals was determined quantitatively (Table 3) where ND indicates not detectable amount.

Results and Discussion

Concentrations of As, Cd, Pb, Cr and Hg in muscle tissue of marine fish samples are shown in Table 3. A graphical representation of heavy metals content is also shown in Figure 2. A comparison between mean value and MRL value is represented in figure 3.

Arsenic Content

Arsenic is a naturally occurring element that is common in soils, water and living organisms. Fish can accumulate considerable amounts of organic arsenic from environment. Most As in our diet is present in organic form. The present study shows As content was in between ND-0.04 mg/kg. Comparatively higher concentration (0.04 mg/kg) of arsenic accumulation was observed in Chingri (M. monoceros) and Poa (B. loach). Lakkaha (E. tetradactylum), koral (L. calcarifer), kalochanda (P. chinensis), undurabaila (P. indicus), loitta (H. nehereus) and shadhachanda (P. argenteus) contain arsenic in very low level. The maximum recommended levels permitted for As in sea fish as 2.00 mg/kg [15]. Comparing the analytical data for As content in marine fish sample with the recommended value, it is clear that the consumption of these marine fish may not any health hazard risks and their consumption may not risky at all. But gradual bioaccumulation due to frequent exposure to arsenic can cause several chronic and acute diseases [19].

Cadmium Content

Cd concentrations in marine fishes were ND-0.19 mg/kg and of mean value 0.04 mg/kg. The highest amount of Cd content was found in the chingri (M. monoceros) fish (0.19 mg/kg).This is because the fact that the chingri (M. monoceros) habitually prefer to live at the sandy and muddy bottoms of the marine ecosystem where toxic and hazardous substances are deposited [20]. Cd was below detection level in koral (L. calcarifer) and tekchanda (P. chinensis). The maximum recommended levels permitted for Cd in sea fish is 0.5-0.6 mg/kg [15]. Thus, all the fish samples analysed in this study may be safe for the public consumption. Long period of accumulation of Cd in fish may pose health hazards. Cd shows no indication of being an essential element in biological processes, instead it is toxic. Cd causes several toxic effects in human body including bone demineralization, renal dysfunction, and lung damage and lung cancer [21]. It competes with the Fe in the body and creates iron deficiency causes slight anaemia [22].

Lead Content

The concentration of Pb in the marine fish samples were found from 0.06-0.35 mg/kg and average Pb in fish is 0.20 mg/kg. The maximum acceptable limit for fish is 2.00 mg/kg [15].Present study indicated that the concentration of Pb levels was lower than permissible limits. Thus, this study confirmed that the consumption of marine fish samples is safe in the context of Pb contamination. Pb exists in nature mainly as lead sulfide. This metal is extremely insoluble and is readily absorbed by organic matter, especially under reducing conditions. Several anthropogenic sources like municipal and industrial wastes, mining, gasoline combustion, smelting and reprocessing action are responsible for the lead contamination in the environment [23]. Several symptoms such as intestinal cramps, fatigue, children mental disorder, hyper tension in expectant women and enzymatic inhalation are caused in human body due to the consumption of highly Pb contaminated fish [24].

Chromium Content

Cr concentration in marine fishes was found from 0.42-0.78 mg/kg of mean value 0.59 mg/kg. In the present study, Cr was found excess than maximum tolerable limit in Ulua (C. carati) 0.78 mg/kg and Teckchanda (L. equulus) 0.76 mg/kg where the lowest amount was in the Shadhachanda (P. argenteus) 0.42 mg/kg. A tolerance level of Cr concentrations in fish is 0.73 mg/kg in fish [17]. Since fish is at the top level of food chain, a higher quantity of Cr bio accumulate in the fish disposed from leather, steel and textile industries including tobacco product where Cr [VI] harmful to human health causing skin diseases, lung cancer, kidney and liver damage, ulcer and mutation in genetic materials [25].

Mercury Content

Hg is one of the most toxic elements. Hg was found from 0.01-0.61 mg/kg in the fish samples and of mean value is 0.19mg/kg. The highest amount (0.61 mg/kg) of Hg content was found in lakkha fish (E. tetradactylum) and lowest amount (0.01 mg/kg) was found in loitta fish (H. nehereus).The joint FAO/WHO expert committee on food additives [16] and ANHMRC (Australian National Health and Medical Research Council) set the standard for Hg in seafood to 0.50 mg/kg. The result indicate that mean Hg level in marine fishes is below FAO/WHO (2011) and ANHMRC permissible limit. After disposal of Hg from different natural (volcanoes, forest fire and fossil fuel) and anthropogenic sources (gold mining, incineration of municipal, hydroelectric, e-waste, pulp and paper industries and medical waste) it deposited in water body where it bioaccumulates in the fish tissues which create toxicity like neurotoxicity, nephrotoxicity and genotoxicity in human body after consuming such fish [26].

Conclusion

The present study reveals several information about the toxicity level of heavy metals bioaccumulation in marine fish of Bay of Bengal. The toxic metals content trend is like Cr >Pb> Hg > Cd > As. The analysed marine fish samples are at the safe level of consumption in the context of As, Cd, Pb, Cr and Hg contamination except Ulua (C. carati) and Teckchanda (L. equulus) fish where only Cr contamination level exceed permissible limit (0.73 mg/kg). Again, this study was compared with the previous study of fresh water fish which implies that the toxic metal contamination of marine fish is lower than fresh water fish and this is may be due to the high dilution factor of marine water. From this study it is seen that the consumption of these species is still in safe level but frequent and excessive consumption of these fish may result in chronic non-carcinogenic effect in human body. Finally it is recommended that a continuous observation should ensure to control the pollution of Bay of Bengal so that toxicity level of heavy metals does not exceed the global permissible limit.

Acknowledgements

Authors are grateful to International Science Program (ISP), Uppsala University, Sweden, HEQEP (Higher Education Quality Enhancement Project) and Ministry of Science and Technology, Government of the People’s Republic of Bangladesh for financial supports.

References

1. Quader O, Coastal and marine biodiversity of Bangladesh (Bay of Bengal) FB08. Proceedings of International Conference on Environmental Aspects of Bangladesh (ICEAB 10). Japan. 2010. p. 83-86.

2. Svensson BG, Nilsson A, Hanson M, Rappe C, Akesson B, Exposure to dioxins and dibenzofurans through the consumption of fish. N Engl J Med, 1991. 324: p. 8-12.

3. Ahmad K, Azizullah A, Shama S, Khattak MNK, Determination of heavy metal contents in water, sediments, and fish of Shizothorax plagiostomus in river Panjkora at Lower Dir, Khyber Pakhtunkhwa. Pakistan. Environ Monit Assess, 2014. 186: p. 7357-7366.

4. MacFarlane GB, Burchettt MD, Cellular distribution of Cu, Pb, and Zn in the Grey Mangrove Avicemnia marina (Forsk.). Vierh Aquatic Botanic, 2000. 68: p. 45–59.

5. Fábio PA, Lourenço AS, Hélio BS, Marcos VTG, Nilo B, Bioaccumulation of mercury, cadmium, zinc, chromium, and lead in muscle, liver and spleen tissues of a large commercially valuable catfish species from Brazil. Anais da Academia Brasileira de Ciências, 2016. P. 1678-2690.

6. Ishaq SE, Rufus SPA, Annune, Bioaccumulation of Heavy Metals in Fish (Tilapia zilli and Clarias gariepinus) Organs from River Benue, North-Central Nigeria Pak. J. Anal. Environ. Chem, 2011. 12(1): p. 225-231.

7. Jayaprabha N, Balakrishnan S, Purusothaman S, Indira K, Srinivasan M, Anantharaman P, Bioaccumulation of heavy metals in flying fishes along southeast coast of India. International Food Research Journal, 2014. 21(4): p. 1381-1386.

8. Opinion of the Scientific Panel on contaminants in the food chain [CONTAM] related to the safety assessment of wild and farmed fish EFSA (2005)

9. Babatunde AM, Abdul MWO, Akinyemi AA, Bioaccumulation of heavy metals in fish (Hydrocynus forskahlii, Hyperopisusbebeoccidentalis and Clarias gariepinus) organs in downstream ogun coastal water, nigeria. Transnational Journal of Science and Technology, edition, 2012. 2(5): p. 119-133.

10. Rahman MS, Molla AH, Saha N, Rahman A, Study on heavy metals levels and its risk assessment in some edible fishes from Bangshi River, Savar, Dhaka, Bangladesh. Food Chemistry, 2012. 134(4): p. 1847-54.

11. Hossain A, Rahman MM, Saha B, Moniruzzaman M, Begum M, Heavy metal concentration and its toxicity assessment in some market fishes of Dhaka city. International Journal of Fisheries and Aquatic Studies, 2016. 4(3): p. 523-527.

12. Saha N, Zaman MR, Safiur MR, Heavy metals in fish, fruits and vegetables from rajshahi, bangladesh: A statistical approach. Journal of Nature Science and Sustainable Technology, 6(3).

13. Ahmed MK, Baki MA, Kundu GK, Islam MS, Islam MM, Hossain MM, Human health risks from heavy metals in fish of Buriganga river, Bangladesh. SpringerPlus, 2016. 5: p. 1697.

14. APHA, AWWA, WPCF, Standard Methods for the Examination of Water and Wastewater. 17th Edn. 1995. Washington, D.C.

15. WHO Guidelines for the study of dietary intakes of chemical contaminants. World Health Organization, Geneva. (1985).

16. WHO Health Criteria Other Supporting Information. In Guidelines for Drinking Water Quality. 3rd ed. Geneva. 1996. 2: 31-388.

17. Wyse EJ, Azemard S, Mora SJ, Report on the World-wide Inter comparison Exercise for the Determination of Trace Elements and Methyl mercury in Fish Homogenate. IAEA-407, IAEA/AL/144 (IAEA/MEL/72), IAEA, Monaco. 2003.

18. Ahmad MK, Islam S, Rahman S, Haque MR, Islam MM, Heavy Metals in Water, Sediment and Some Fishes of Buriganga River, Bangladesh. Int. J. Environ. Res, 2010. 4(2): p. 321-332.

19. Ahmed MK, Baki MA, Islam MS, Kundu GK, Al-Mamun MH, Human health risk assessment of heavy metals in tropical fish and shellfish collected from the river Buriganga, Bangladesh. Environ Sci Pollut Res Int , 2015. 20: p. 15880-15890.

20. Alina M, Azrina A, Mohd Yunus AS, Mohd Zakiuddin S, Effendi MH, Rizal RR, Heavy metals (mercury, arsenic, cadmium, plumbum) in selected marine fish and shellfish along the Straits of Malacca. International Food Research Journal, 2012. 19(1): p. 135-140.

21. Judilyn MS, De Vera MJD, Abdulla ADC, Evangelista JH, Ann VMJ Nerosa. Quantitative Analysis of Lead, Cadmium and Chromium found in Selected Fish marketed in Metro Manila, Philippines. International Journal of Environmental Science and Development, 2013 4(2): p. 207-212

22. Lauwerys RR, Health effect of cadmium in trace metals exposure and health effects. Published by Pergaman Presspp, 1979. p. 107-116.

23. Krishna PV, Jyothirmayi V, Rao KM, Human health risk assessment of heavy metal accumulation through fish consumption, from Machilipatnam Coast, Andhra Pradesh, India. International Research Journal of Public and Environmental Health, 2014.1 (5): p.121-125.

24. Krishna PV, Swapna CH, Prabhavathi K, Panchakshari V, Heavy metal accumulation in Channa striata from Kolleru Lake and human health risk assessment. International Journal of Advanced Research, 2015. 3(8): p.994–998.

25. Afshan S, Ali S, Ameen US, Farid M, Bharwana SA et al; Effect of Different Heavy Metal Pollution on Fish. Research Journal of Chemical and Environmental Sciences Res. J. Chem. Env. Sci, 2014. 2(1): p. 74-79.

26. Shoeb M, Hossain MA, Kibria MG, Mustafa T, Nahar N, Bioaccumulation of Mercury in Fish Species from Different Trophic Level. Journal of Food Science and Engineering, 2017. p. 363-367.

PEER REVIEW

Not commissioned. Externally peer reviewed.

Table 2. Analytical parameters for the measurement of toxic metals.

Table 3. Concentration of heavy metals (mg/kg fresh weight) in the tissues of marine fish and their Maximum Tolerable Limit.

Table 4. Comparison of toxic metals between fresh and marine fish of Bangladesh (mg/kg).

References

1. Quader O, Coastal and marine biodiversity of Bangladesh (Bay of Bengal) FB08. Proc of International Conference on Environmental Aspects of Bangladesh (ICEAB 10). Japan. 2010. p. 83-86.
2. Svensson BG, Nilsson A, Hanson M, Rappe C, Akesson B, Exposure to dioxins and dibenzofurans through the consumption of fish. N Engl J Med, 1991. 324: p. 8-12.
3. Ahmad K, Azizullah A, Shama S, Khattak MNK, Determination of heavy metal contents in water, sediments, and fish of Shizothorax plagiostomus in river Panjkora at Lower Dir, Khyber Pakhtunkhwa. Pakistan. Environ Monit Assess, 2014. 186: p. 7357-7366.
4. MacFarlane GB, Burchettt MD, Cellular distribution of Cu, Pb, and Zn in the Grey Mangrove Avicemnia marina (Forsk.). Vierh Aquatic Botanic, 2000. 68: p. 45–59.
5. Fábio PA, Lourenço AS, Hélio BS, Marcos VTG, Nilo B, Bioaccumulation of mercury, cadmium, zinc, chromium, and lead in muscle, liver and spleen tissues of a large commercially valuable catfish species from Brazil. Anais da Academia Brasileira de Ciências, 2016. P. 1678-2690.
6. Ishaq SE, Rufus SPA, Annune, Bioaccumulation of Heavy Metals in Fish (Tilapia Zilli and ClariasGariepinus) Organs from River Benue, North-Central Nigeria Pak. J. Anal. Environ. Chem, 2011. 12(1): p. 225-231.
7. Jayaprabha N, Balakrishnan S, Purusothaman S, Indira K, Srinivasan M, Anantharaman P, Bioaccumulation of heavy metals in flying fishes along southeast coast of India. International Food Research Journal, 2014. 21(4): p. 1381-1386.
8. Opinion of the Scientific Panel on contaminants in the food chain [CONTAM] related to the safety assessment of wild and farmed fish EFSA (2005)  
9. Babatunde AM, Abdul MWO, Akinyemi AA, Bioaccumulation of heavy metals in fish (hydrocynusforskahlii, hyperopisusbebeoccidentalisandclariasgariepinus) organs in downstream ogun coastal water, nigeria. Transnational Journal of Science and Technology, edition, 2012. 2(5): p. 119-133.
10. Rahman MS, Molla AH, Saha N, Rahman A, Study on heavy metals levels and its risk assessment in some edible fishes from Bangshi River, Savar, Dhaka, Bangladesh. Food Chemistry, 2012. 134(4): p. 1847-54.
11. Hossain A, Rahman MM, Saha B, Moniruzzaman M, Begum M, Heavy metal concentration and its toxicity assessment in some market fishes of Dhaka city. International Journal of Fisheries and Aquatic Studies, 2016.  4(3): p. 523-527.
12. Saha N, Zaman MR, Safiur MR, Heavy metals in fish, fruits and vegetables from rajshahi, bangladesh: A statistical approach. Journal of Nature Science and Sustainable Technology, 6(3).
13. Ahmed MK, Baki MA, Kundu GK, Islam MS, Islam MM, Hossain MM, Human health risks from heavy metals in fish of Buriganga river, Bangladesh. SpringerPlus, 2016. 5: p. 1697.
14. APHA, AWWA, WPCF, Standard Methods for the Examination of Water and Wastewater. 17th Edn. 1995. Washington, D.C.
15. WHO Guidelines for the study of dietary intakes of chemical contaminants. World Health Organization, Geneva. (1985).
16. WHO Health Criteria Other Supporting Information. In Guidelines for Drinking Water Quality. 3rd ed. Geneva. 1996. 2: 31-388.
17. Wyse EJ, Azemard S, Mora SJ, Report on the World-wide Inter comparison Exercise for the Determination of Trace Elements and Methyl mercury in Fish Homogenate. IAEA-407, IAEA/AL/144 (IAEA/MEL/72), IAEA, Monaco. 2003.
18. Ahmad MK, Islam S, Rahman S, Haque MR, Islam MM, Heavy Metals in Water, Sediment and Some Fishes of Buriganga River, Bangladesh. Int. J. Environ. Res, 2010. 4(2): p. 321-332.
19. Ahmed MK, Baki MA, Islam MS, Kundu GK, Al-Mamun MH, Human health risk assessment of heavy metals in tropical fish and shellfish collected from the river Buriganga, Bangladesh. Environ Sci Pollut Res Int , 2015. 20: p. 15880-15890.
20. Alina M, Azrina A, MohdYunus AS, MohdZakiuddin S, Effendi MH, Rizal RR, Heavy metals (mercury, arsenic, cadmium, plumbum) in selected marine fish and shellfish along the Straits of Malacca. International Food Research Journal, 2012. 19(1): p. 135-140.
21. Judilyn MS, De Vera MJD, Abdulla ADC, Evangelista JH, Ann VMJ Nerosa. Quantitative Analysis of Lead, Cadmium and Chromium found in Selected Fish marketed in Metro Manila, Philippines. International Journal of Environmental Science and Development, 2013 4(2): p. 207-212
22. Lauwerys RR, Health effect of cadmium in trace metals exposure and health effects. Published by Pergaman Presspp, 1979. p. 107-116.
23. Krishna PV, Jyothirmayi V, Rao KM, Human health risk assessment of heavy metal accumulation through fish consumption, from Machilipatnam Coast, Andhra Pradesh, India. International Research Journal of Public and Environmental Health, 2014.1 (5): p.121-125.
24. Krishna PV, Swapna CH, Prabhavathi K, Panchakshari V, Heavy metal accumulation in Channa striata from Kolleru Lake and human health risk assessment. International Journal of Advanced Research, 2015. 3(8): p.994–998.
25. Afshan S, Ali S, Ameen US, Farid M, Bharwana SA et al; Effect of Different Heavy Metal Pollution on Fish. Research Journal of Chemical and Environmental Sciences Res. J. Chem. Env. Sci, 2014. 2(1): p. 74-79.
26. Shoeb M, Hossain MA, Kibria MG, Mustafa T, Nahar N, Bioaccumulation of Mercury in Fish Species from Different Trophic Level. Journal of Food Science and Engineering, 2017. p. 363-367.